This invention relates to neutron detecting. Specifically, this invention relates to icosahedral boride semiconducting materials for neutron detection applications and methods of use.
The neutron is a sub-atomic particle which has mass, but no electrical charge. Since neutrons have no electrical charge, they cannot directly produce ionization in detectors. Therefore, neutrons cannot be directly detected. In other words, neutrons are difficult to detect, because they are not charged and thus do not interact electrically with most matter as electrons or protons do. As a result, neutron detectors must rely upon a conversion process upon which the presence of neutrons is deduced. In the conversion process, an incident neutron interacts with a nucleus to produce a secondary charged particle. The resulting charged particles can then be directly detected.
Neutrons are produced by fission of nuclear materials or by naturally-occurring radioactive decay. Detection of neutrons at transportation hubs in shipping containers or luggage can indicate the possible presence of smuggled nuclear materials or hidden nuclear weapons (WMDs). Practical, inexpensive solid state neutron detectors could have great application for Homeland Security, Antiterrorism, Nuclear Non-Proliferation applications, nuclear stockpile stewardship programs, nuclear power applications, Occupational Safety for any industry or research applications in which people work with or near fissionable material, nuclear reactors, or high energy accelerators, thermal neutron radiography, which is a powerful inspection/evaluation technique in industry and manufacturing, and they could even be fabricated into microminiaturized arrays to be used as detectors for high energy physics experiments among many other uses.
The need for neutron detectors has escalated in recent years. With the growing threat of terrorists trying to detonate a so-called dirty bomb containing radioactive material, improved devices for detecting plutonium from its neutron emissions are in great need.
Conventional neutron detectors employ high voltages in large gas-filled units. Neutron detection devices have been created using materials such as cadmium zinc telluride, however, neutron capture process produces high energy gamma rays which require the detectors to be large in order to detect the gamma rays efficiently.
Solid state neutron detectors could be mass produced with microfabrication techniques like those used in the semiconductor electronics industry. Additionally, they could be made inexpensive, miniaturized, portable, and operate on conventional low electronics voltages. Thus, they could greatly widen the practical applications for neutron detectors. One example is shown in U.S. Pat. No. 6,771,730 to Dowben, which is herein incorporated by reference in its entirety and can be modified to incorporate this invention.
Studies have shown that boron, with a high neutron capture cross-section should therefore be good for solid-state detectors if suitable semiconductor materials can be developed. Boron-based neutron detectors have been created using materials such as pyrolytic boron nitride (BN), boron phosphide (BP), boron carbide (B4C). However, these materials have all formed relatively inefficient detectors. One example is shown in U.S. Pat. No. 6,771,730 to Dowben, which can be modified to incorporate this invention and is herein incorporated by reference in its entirety.
Prior attempts to develop a suitable detector material have either not worked at all, or had low sensitivity and suffered from the difficulties outlined above. Moreover, additional difficulties or complications encountered in the prior art include multiphase, rather than single phase material, great variability of properties, large lattice mismatch on Si substrates, a high lattice strain, rapid accumulation of radiation damage, or in the case of non-boron-based materials, a much lower neutron capture cross-section, large detector size, or stability problems They furthermore require the use of hazardous, toxic gasses either in the operation or fabrication of the materials. The materials of this invention show potential for improvement over the prior art because of these and other reasons.
Therefore, an improved icosahedral boride semiconducting material for neutron sensing applications and methods of use is desirable.
In light of the foregoing, the primary feature or advantage of the current invention is to provide an improved icosahedral boride semiconducting material for neutron sensing applications and methods of use.
Another feature or advantage of this invention is a material which possesses higher volumetric density of boron atoms than other boride-based neutron detector materials.
Another feature or advantage of the current invention is a material which can be easily made an n-type semiconducting boron-rich boride.
Another feature or advantage of the current invention is a material which can exhibit relatively high charge carrier mobility in either crystallized or amorphous form.
Another feature or advantage of the current invention is a material which is homogeneous, not multiphase, and in its amorphous form, does not possess grain boundaries.
Another feature or advantage of this invention is a material which, in its amorphous form, is more robust to radiation damage, more robust to the lithium by-products produced by nuclear reactions changing the doping, and easier to mass produce over the prior art.
A further feature or advantage of this invention is a material which, in its crystalline form, shows less lattice strain for growth on silicon (100) than other β-based materials.
Still another feature or advantage of this invention is a safer, non-toxic, more environmentally friendly method of fabrication than the prior art.
One or more of these or other features or advantages of the invention will be apparent from the specification and claims that follow.